Microsoft's SQL sets the standard for data handling, as the number one selling SQL server product on the market today.
Advantages of MSSQL include:
Reliability:    MSSQL is reliable, with many built-in features designed to keep your database records intact and healthy.
Scalability:    MSSQL can grow as your company grows.
Linkability:   MSSQL can replicate data between sites, makeing multi-site capability simple and reliable.
See http://www.microsoft.com/sql/default.mspx for additional information about SQL.